The proposed study is the first phase of a multicenter randomized clinical trial, designed to assess the efficacy of different forms of dietary intervention in preventing the development of hypertension. The first phase of the trial will test the feasibility of a full-scale trial which may involve as many as 6,000 participants and a minimum of five years of follow-up for the clinical event of interest -- sustained hypertension requiring initiation of anti-hypertensive treatments. The first phase will involve four clinical centers who are to recruit 800 men and women aged 18-40 years, at entry. The participants will be at high risk by virtue of high-normal diastolic blood pressures and increased relative weight. Approximately half will also have a familial predisposition to hypertension. They will be randomly allocated to a control treatment or one of four dietary interventions: 1) sodium (Na) consumption reduced to less than 70 mEq/day; 2) Na less than 70 mEq/day and potassium supplementation; 3) caloric restriction to achieve "normal" body weight; or 4) a combination of Na and caloric restrictions. The trial includes a Data Coordinating Center, Nutrition and Education Resources Center, a Central Biochemistry Laboratory and Food Record Coding Center. Support is requested to provide sufficient time to collect data to make a judgement whether a full-scale second phase trial is feasible and to close-out this trial if funding for the full-scale trial is not approved.